The present invention relates to a method for screening for a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract. The present invention further relates to a method for screening for culture conditions that provide a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract. The present invention further relates to a method for modulating the expression of certain polynucleotides. The present invention further relates to a method for the preparation of a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract. The present invention further relates to a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract. The present invention further relates to a method for the preparation of a food composition. The present invention further relates to a food composition. The present invention further relates to the use of certain polynucleotides in the screening for a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract and/or the screening for culture conditions that provide a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract and/or for the control of culture conditions providing a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract. The present invention further relates to a method for controlling culture conditions providing a bacterium exhibiting enhanced survival properties in the gastro-intestinal tract.L'invention concerne une méthode de dépistage d'une bactérie possédant des propriétés de survie améliorées dans le tractus gastro-intestinal. L'invention porte également sur une méthode de dépistage de conditions de culture produisant une bactérie possédant des propriétés de survie améliorées dans le tractus gastro-intestinal. L'invention se rapporte encore à une méthode de modulation de l'expression de certains polynucléotides ainsi qu'à une méthode de préparation d'une bactérie posséd
